New narcotic antagonists, particularly those with substituents at the C14 position of the morphinan nucleus, will be synthesized and evaluated as possible prophylactic agents against readdiction in post-addicts. Spin-labelled narcotics and narcotic antagonists will be synthesized in the expectation that they will prove useful in the delineation of the morphine receptor site in the central nervous system. New highly rigid derivatives of thebaine will be synthesized for evaluation as narcotics and narcotic antagonists.